The invention relates to an apparatus and a process for producing shaped parts having the features of the generic part of the independent patent claims. The apparatus and process are suitable in particular for pressure die casting in a cold-chamber process, in particular for the pressure die casting of aluminum. Pressure die casting is an economical production process which is in widespread use for the production of shaped parts. In this process, a melt of the material which is to be shaped is introduced into a shot sleeve and moved in the direction of a die by means of an injection plunger in the shot sleeve. The movement of the melt in the shot sleeve is initially relatively slow. Ultimately, the melt is forced into the die under pressure in what is known as a shot.
One problem with processes of this type is that the melt contains gases which if possible should be removed from within the melt during the movement of the melt. Since the surface of the melt is in contact with cold walls in the shot sleeve, a skin is formed on the surface of the melt. Consequently, gases contained in the melt find it difficult to escape. This can give rise to quality problems.
It has long been known to use vibrations to improve the workpiece quality in casting processes. For example, it is known from JP 60 250 866 to provide a plunger rod with a pressure head having a resonator. The resonator generates a high-frequency oscillation which is transmitted to the melt via the head. The intention is for the melt to penetrate even into thin gaps in the die.
WO 2004/09273 discloses an apparatus for forming a crystallizable material in the liquid or pasty state. According to this disclosure, the material is made to oscillate, at least in some regions, before and/or during forming and/or solidification. The document proposes, inter alia, connecting an oscillation generation unit to the hydraulic pressure line which is used to move the injection plunger.
However, these known apparatuses all have certain drawbacks. In particular, it is difficult to use the hydraulic pressure line to transmit oscillations to the injection plunger sufficiently quickly and in a sufficiently controlled fashion. Moreover, it is complex and expensive to adapt the hydraulic system.
Considerable acceleration forces act on the injection plunger during the shot of the melt into the die. Consequently, there is a risk of oscillation units which act on the injection plunger as shown in JP 60 250 866 A being destroyed.